AISC LRFD 1.pdf

10Chap. BCHAPTER BDESIGN REQUIREMENTSThis chapter contains provisions which are common to the Specification as a whole.B1. GROSS AREAThe gross area A g of a member at any point is the sum of the products of the thicknessand the gross width of each element measured normal to the axis of themember. For angles, the gross width is the sum of the widths of the legs less thethickness.B2. NET AREAThe net area A n of a member is the sum of the products of the thickness and the netwidth of each element computed as follows:In computing net area for tension and shear, the width of a bolt hole shall be taken as1 16 -in. (2 mm) greater than the nominal dimension of the hole.For a chain of holes extending across a part in any diagonal or zigzag line, the netwidth of the part shall be obtained by deducting from the gross width the sum of thediameters or slot dimensions as provided in Section J3.2, of all holes in the chain,and adding, for each gage space in the chain, the quantity s 2 / 4gwheres = longitudinal center-to-center spacing (pitch) of any two consecutive holes,in. (mm)g = transverse center-to-center spacing (gage) between fastener gage lines, in.(mm)For angles, the gage for holes in opposite adjacent legs shall be the sum of the gagesfrom the back of the angles less the thickness.In determining the net area across plug or slot welds, the filler metal shall not beconsidered as adding to the net area.B3. EFFECTIVE AREA OF TENSION MEMBERSThe effective area of tension members shall be determined as follows:(1) When tension load is transmitted directly to each of the cross-sectional elementsby fasteners or welds, the effective area A e is equal to the net area A n .(2) When the tension load is transmitted by fasteners or welds through some butnot all of the cross-sectional elements of the member, the effective area A e shallbe computed as follows:LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION